Climate and Phytogeography
Kish Island is located in a narrow strip of land of the Northern Hemisphere’s tropical-subtropical flora, at a low geographic latitude, between the Iranian Plateau (to the north) and the Arabian Desert (to the south). Apart from local geographic and climatic peculiarities, this island, like its neighboring islands, is under the influence of the semi-equatorial climatic conditions of this floral strip. The island’s climate is classified according to the combined effects of precipitation and temperature. That is, the ratio of rainfall in millimeters to the temperature in degrees over the year is determined, and if the amount of rainfall is less than twice the temperature, that climate is considered arid. Kish is situated in a very dry region and its overall climatic conditions are arid and semi-equatorial. The average rainfall for the past year according to statistics is 3.6 mm and its average maximum temperature is 32.5 degrees Celsius.
The state of relative humidity of the atmosphere and the coefficient of prevailing climatic conditions have made its weather maritime. Except during the cold season days, the humidity is above 60 percent for the rest of the year. From Aban to Ordibehesht (approximately November to May) Kish’s weather is mild and its temperature fluctuation is between 18–25 degrees Celsius. According to available statistics, Kish’s climate is very hot to warm-moderate, accompanied by high relative humidity and sometimes rains of variable intensity and often short duration on some days of the year.
In the usual climatic classifications and according to climatic factors and elements, especially because of its proximity to the Tropic of Cancer and exposure to the subtropical high-pressure system and having local positional characteristics of being in the warm and shallow waters of the Persian Gulf and under the influence of its climatic conditions, Kish is naturally warm and often humid in most days of the year.
Kish’s precipitation usually occurs from Azar to Esfand (approximately December to March). Azar rains are roughly irregular and of variable intensity. But Esfand rains are regular and relatively stable. Relative multi-year estimates show that the rainy season usually begins in Aban (approximately November) and ends around Ordibehesht (approximately May) and the total rainy periods amount to a few hours distributed over several days.
In the past, given that Kish Island lies in the tropical floral strip, occasional penetration of seasonal Indian Ocean flows, especially in Mordad (approximately August) when these flows peak, has caused sporadic, rapid, short summer showers in the form of heavy downpours. The amount of summer precipitation on Kish sometimes exceeds the total annual precipitation and is usually flood-like.
The annual precipitation relative to annual evaporation always indicates the climatic situation of any region, and if the minimum evaporation of a region is more than ten times its precipitation (as in deserts or most central parts of Iran), that climate is dry, hot and barren. But Kish, due to its local position in the warm, shallow waters of the Persian Gulf with high humidity close to saturation, which causes its air to be humid in most days of the year, has a maritime climate and weather.